Holt McDougal Geometry

3-1 Lines and Angles

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Pg. 148 (14-29; 44 why4; 55-62)

Holt McDougal Geometry

3-1 Lines and Angles

How do you identify parallel, perpendicular, and skew lines?

How do you identify the angles formed by two lines and a transversal?

Essential Questions

Holt McDougal Geometry

3-1 Lines and Angles

Holt McDougal Geometry

3-1 Lines and Angles

Segments or rays are parallel, perpendicular, or skew if the lines that contain them are parallel, perpendicular, or skew.

Helpful Hint

Holt McDougal Geometry

3-1 Lines and Angles

Example 1: Identifying Types of Lines and Planes

Identify each of the following.

A. a pair of parallel segments

B. a pair of skew segments

C. a pair of perpendicular segments

D. a pair of parallel planes

LM ||QR

KN and PQ

NS ⊥ SP

plane NMR || plane KLQ

Holt McDougal Geometry

3-1 Lines and Angles

Holt McDougal Geometry

3-1 Lines and Angles

Example 2: Classifying Pairs of Angles

Give an example of each angle pair.

A. corresponding angles

B. alternate interior angles

C. alternate exterior angles

∠1 and ∠5

D. same-side interior angles

∠3 and ∠5

∠1 and ∠7

∠3 and ∠6

Holt McDougal Geometry

3-1 Lines and Angles

To determine which line is the transversal for a given angle pair, locate the line that connects the vertices.

Helpful Hint

Holt McDougal Geometry

3-1 Lines and Angles

Example 3: Identifying Angle Pairs and Transversals

Identify the transversal and classify each angle pair.

A. ∠1 and ∠3

B. ∠2 and ∠6

C. ∠4 and ∠6

transversal l

corr. ∠s

transversal nalt. int ∠s

transversal malt. ext ∠s